1. Field of the Invention
This invention relates to material handling vehicles and, more particularly, to a material handling vehicle for use in highway, off-road and railroad applications which includes a single engine that may be controlled from multiple operator's stations.
2. Description of the Prior Art
Heretofore, material handling vehicles such as excavators or cranes have been developed for use on highways and on railroad tracks. Such vehicles typically include a lower or truck chassis on which there is pivotally mounted an upper structure that supports a material handling implement. The lower chassis is capable of being driven over the road or highway under the control of an operator in a cab mounted on the lower chassis. The lower chassis additionally includes deployable railroad wheels to guide the vehicle's movement along railroad tracks with driving power being provided by the engagement of the drive wheels of the lower chassis with the railroad tracks. An upper structure is mounted on the lower chassis by a swing bearing through which a center pin extends for relative movement with respect to the lower chassis. An upper structure operator's cab is provided on the upper structure as well as a material handling boom and implement. During operation on railroad tracks, an operator in the upper structure operator's cab can control movement of the lower chassis and also of the material handling implement.
Previously, in order to provide power for remote operation under the control of an operator in the upper structure cab of both the manipulations of the material handling implement as well as the movement of the vehicle along the railroad tracks, two separate engines were required. One engine was mounted on the lower chassis and controlled the highway operation of the vehicle. A separate engine was mounted on the upper structure and provided power to the material handling mechanism as well as powering, through a hydraulic pump and motor, the motion of the lower chassis.
As is well known in the art, the previously unavoidable requirement of two separate engines, one on the truck chassis and one on the upper structure, was fraught with a host of disadvantages. For example, in the prior art construction requiring two separate engines, the additional weight and cost of the auxiliary engine itself as well as duplicate fuel tanks, radiators, batteries and charging systems, air compressors and dryers, power steering pumps, air cleaners and exhaust systems, controls, shroudings and mountings, noise barriers, engine gauges, etc. are incurred. In addition, duplicate maintenance functions are involved in a two-engine vehicle and operating costs are necessarily increased. Further, the inclusion of the second engine and hydraulic reservoir on the movable upper structure raised the center of gravity of such material handling vehicles. Such a high center of gravity imposed engineering and operating restrictions which were considerable.
It is apparent that for a material handling vehicle to be effective for railroad applications, it must have the capability of pulling railroad cars along the tracks. For example, in the case of an excavating vehicle, the apparatus should have the capability of pulling a hopper car along the tracks which may be filled with material removed by the excavator. Prior art two-engine excavating vehicles provided alternative means for powering the vehicle's movement along railroad tracks. In one operating mode, an operator in the lower operator's cab could drive the lower chassis while pulling a railroad car. While this mode of operation provided sufficient power to allow the vehicle to pull a railroad car, an operator who was in the upper cab would have to move to the lower cab to control vehicle travel on the railroad tracks. If excavating was to be performed during travel on railroad tracks, because all excavator functions were controlled from the upper structure operator's cab, a second operator in the upper structure cab was required to manipulate the material handling implement under the power of the upper structure engine. As such, in that operating mode, both engines were running and two operators were required. If only a single operator were present in the upper structure operator's cab, and the upper structure engine was actuated to provide power to a hydraulic pump to power the material handling implement functions as well as power the vehicle by a hydraulic motor, the power required to move a railroad car would not be available. Accordingly, prior art two-engine excavators have proven unsuitable for use in railroad applications.
The assignee of the present invention has developed an alternative method of powering a material handling vehicle for use in highway and off-road, but primarily not railroad, applications. This apparatus, disclosed in U.S. patent application Ser. No. 807,616, filed Dec. 11, 1985, now U.S. Pat. No. 4,705,450, relates to a material handling vehicle having a lower chassis which includes an engine and a first operator's cab. An upper structure is pivotally mounted on the lower chassis and includes an upper structure operator's cab and a material handling implement. Such a vehicle may be powered in one of two ways. First, an operator in the lower cab may control the engine so as to drive through a powershift transmission to power the drive wheels of the vehicle. If operation is intended from the upper structure operator's cab, by the proper control of the powershift transmission, the engine is effectively disconnected from the transmission and, instead, drives a hydraulic pump. The hydraulic pump may power the excavator functions and supply hydraulic fluid under pressure to a hydraulic motor. The hydraulic motor may then be caused to drive a secondary input into the powershift transmission to cause it to generate a rotational output effective to drive the vehicle's drive wheels.
However, such a vehicle also suffers shortcomings when considered for use in railroad applications. Only two modes of operating and powering such a vehicle would be possible in a railroad application. In one operating mode, an operator in the lower truck cab could drive the vehicle with the engine directly coupled to the transmission to power the vehicle. In this mode, sufficient power would be available to tow a railroad car. However, no excavator functions would be possible. In an alternative operating mode, an operator in the upper cab could control the movement of the vehicle under driving power provided by the engine through the hydraulic pump and motor into the transmission. However, because of the limited capacity of the hydraulic motor, the vehicle would not possess sufficient power to pull a railroad car. Accordingly, while the single engine material handling vehicle eliminates certain of the problems associated with two-engine excavators, such a vehicle is unsuitable for complete railroad operation.
The subject invention is directed toward an improved material handling apparatus which overcomes, among others, the above discussed problems with material handling vehicles intended for use on railroad tracks and which is effective to sufficiently power the vehicle to allow control by one operator of a vehicle having sufficient power to tow a railroad vehicle and control the material handling implement functions.